Clinical Rehabilitation

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1 The effects of Transcutaneous Electrical Nerve Stimulation (TENS) on strength, proprioception, balance and mobility in people with stroke Journal: Clinical Rehabilitation Manuscript ID: Draft Manuscript Type: Original Article Keywords: Balance, TENS (transcutaneous electrical nerve stimulation), Mobility, Stroke, Proprioception Abstract: Background: Transcutaneous electrical nerve stimulation (TENS) promotes cortico-excitability which has the potential to improve function if used while active Objective: To investigate the feasibility and potential efficacy of active TENS (that is TENS during everyday activities) on strength, proprioception, balance/ falls risk and mobility after stroke Method: Design: A paired-sample randomised cross-over trial. No stimulation was the control. Intervention: A single session of active TENS via a sock electrode (0-0Hz, second cycle) plus a session of control treatment (no stimulation). Participants: chronic stroke survivors with no pre-existing conditions limiting balance or mobility or contra-indications to TENS. Outcomes: Dorsiflexor and plantarflexor strength and proprioception using an isokinetic dyanometer, balance/ falls risk (standing forward reach test) and gait speed (0m walk test). Analysis: Paired t-tests and mean and percentage differences to assess the effects of intervention and linear regressions characterise potential responders Results: All participants tolerated active TENS. All parameters improved with TENS (p= ) except dorsiflexor strength (p=0.) and dorsiflexion proprioception (p=0.0).. Conclusions: The results provide initial evidence of the potential of active TENS to benefit physical function after stroke which warrants further PHASE II trials to develop the intervention. Concerns that stimulation should increase risk of falls were not supported

2 Page of Clinical Rehabilitation ABSTRACT Background: Transcutaneous electrical nerve stimulation (TENS) promotes corticoexcitability which has the potential to improve function if used while active Objective: To investigate the feasibility and potential efficacy of active TENS (that is TENS during everyday activities) on strength, proprioception, balance/ falls risk and mobility after stroke Method: Design: A paired-sample randomised cross-over trial. No stimulation was the control. Intervention: A single session of active TENS via a sock electrode (0-0Hz, second cycle) plus a session of control treatment (no stimulation). Participants: chronic stroke survivors with no pre-existing conditions limiting balance or mobility or contraindications to TENS. Outcomes: Dorsiflexor and plantarflexor strength and proprioception using an isokinetic dyanometer, balance/ falls risk (standing forward reach test) and gait speed (0m walk test). Analysis: Paired t-tests and mean and percentage differences to assess the effects of intervention and linear regressions characterise potential responders Results: All participants tolerated active TENS. All parameters improved with TENS (p= ) except dorsiflexor strength (p=0.) and dorsiflexion proprioception (p=0.0).. Conclusions: The results provide initial evidence of the potential of active TENS to benefit physical function after stroke which warrants further PHASE II trials to develop the intervention. Concerns that stimulation should increase risk of falls were not supported

3 Page of INTRODUCTION Transcutaneous Electrical Nerve Stimulation (TENS) increases cortico-motor excitability of the areas for the body part(s) that have been stimulated and the excitability may outlast the period of stimulation -. Hence it is postulated that supplementing sensory input using TENS may facilitate long-term neuro-plastic changes and enhance motor recovery after stroke. It is readily available, inexpensive and relatively easy to apply so, if effective, would be relatively simple to use as part of a rehabilitation programme or in everyday life. Several trials have suggested that TENS applied to the lower limb can have beneficial effects on spasticity, strength and mobility but, systematic reviews have concluded that further trials are needed to overcome methodological short-comings and develop the intervention more thoroughly,. One potentially important aspect of that development is to consider how the TENS is delivered. Previous trials of TENS for people with stroke, have delivered the TENS contemporaneously but separately to therapy or training sessions - or with no other treatment,. In providing the stimulation while inactive, these trials may have limited the effect as the cortical activation during treatment is related to the functional gain ; indicting that it would be desirable to deliver TENS in ways that maximises excitation during treatment. Furthermore, it is important for functional recovery to practice in a relevant environment so that improvements carry over into every-day life. Thus we hypothesise that TENS may enhance everyday activity if used during everyday activities, rather than while inactive. Our aim is therefore to investigate the feasibility and potential efficacy of TENS during every-day life (or active TENS ) on lower limb impairments (strength, proprioception) and activity limitations (balance and mobility). Although there is a good theoretical rationale and some evidence for this from a previous case report, there is an alternative argument that supplementary stimulation while active could be harmful as the additional attentional demand of perceiving the supplementary sensory stimulation could

4 Page of Clinical Rehabilitation distract a stroke survivor s capacity to balance or walk safely. Thus, in line with the MRC Framework for the Development and Evaluation of Complex Interventions we undertook an exploratory trial of active TENS of the effect on falls risk to tell us whether we should precede to further trials and, if so, to obtain data to inform the choice of parameters and sample size calculations for future trials. METHOD A paired sample, randomised cross-over trial of the immediate effects of TENS was used in which the participants acted as their own control and the randomisation came from the order in which the TENS or control was given (which provided blinded allocation of which treatment came first). Blinded group allocation was not an issue as all patients received both the control and stimulation condition. All participants completed both control and stimulation conditions and all testing procedures. To blind the participants as far as possible to the treatment received, they were told that they would receive two types of stimulation which they may, or may not, be able to feel without specifying which we thought may be the more effective. Further details of the randomisation process are found in the section on the testing protocol and outcome measures The Participants: After ethical approval from the University s Research Ethics Panel, we recruited a convenience sample of stroke survivors through local community stroke groups and/or the research group s database of study volunteers. They were communitydwelling stroke survivors, who had completed their rehabilitation, had enduring balance and/or mobility limitations but were able to stand for at least 0 seconds without assistance (with walking aids if necessary), able to consent and travel to the University s clinical research facility for testing and had no pre-existing conditions limiting balance or mobility or contradictions to TENS to the leg (cardiac pacemaker or skin lesions over the lower leg).

5 Page of The intervention: The TENS was delivered using a Biostim M TENS unit (Biomedical Life Systems, Princeton, USA) with a conductive (ankle length) sock that stimulates the whole foot and ankle. Participants wore conductive socks on both feet but only the one on the affected foot was connected to the TENS machine (isock, TensCare Ltd, Surrey, UK). The sock has the advantages that it is easier put on than gel electrodes and does not produce the allergic reactions occasionally seen with gel electrodes and enables a larger area of stimulation, which is desirable -,, 0. The sock s manufacturer recommends that it should be dampened to maximise conductivity of the stimulation. However pilot work showed that this was impossible to standardise and participants found it unacceptable to wear a damp sock inside their shoe, so the sock was used in a dry condition. A biphasic symmetrical stimulus with phase duration of 0µs and ranging frequency of 0-0Hz over a second cycle was used. This frequency modulation was to prevent habituation of receptors and cover the optimal frequency for all participants which is specific to each individual but is around 00 Hz. Stimulation intensity was increased until each participant reported a comfortable tingling or buzzing feeling over their foot and/or ankle without muscle activation or radiation to proximal body segments. Participants were encouraged to increase the stimulation if they felt it was wearing off during the session; however none felt the need to do so. As our goal was to develop the intervention during everyday activities we did not specify the duration of the stimulation but encouraged participants to move around and use it until they felt comfortable and had got used to the sensation then we tested them while stimulated. Equally, when tested without the stimulation (the control condition) they indicated when they felt the stimulation had worn off and were then tested. For the control treatment, the sock and TENS was applied in the same way and the machine was turned on but no stimulation was given. During this familiarisation period, most participants walked around the building or the movement laboratory and/or practiced balance tasks (such as

6 Page of Clinical Rehabilitation shifting their weight from one foot to another). Some went to the toilet and others went to the café for a cup of tea. We did not formally record the activity or length of time taken. Testing protocol and outcome measures: All testing was completed in a single session. After informed consent was obtained, the TENS socks were put on, the TENS machine was attached to the sock on the weak side and the participant was randomised (by them selecting a concealed envelope from a bag) to receive either the stimulation or the control condition first. Once the TENS had been set up, the participant was encouraged to move and walk around to familiarise themselves with the sock (+/- the stimulation). Once they felt comfortable and confident the following testing protocol was undertaken. The order of tests performed with and without TENS stimulations was block randomised to avoid any order effect. The testing using the Biodex Isokinetic Dyanometer (ankle proprioception and strength) was completed in one block and the balance and mobility tests in another. The participants were free to move around or rest at their convenience during and in-between the testing. Measurement Tools: For all parameters, the test was explained and demonstrated to the participant who then practiced as often as they liked until they felt comfortable. The isokinetic dyanometer tests were repeated six times (three in each direction in random order) and mean values were calculated. The falls risk/ balance and mobility tests were measured twice and mean values calculated after an initial practice run Proporioception detection threshold was assessed by evaluating joint position sense of the ankle in dorsiflexion and plantarflexion using a Biodex Isokinetic Dyanamoeter. Participants sat in the Biodex chair with their eyes closed to eliminate visual input and their weak foot was placed on the footplate and their position was adjusted so that the knee was comfortable (~0 degrees flexion) and secured with a Velcro belt across the chest, pelvis and

7 Page of thigh. The participants ankle was passively moved from a neutral position in to either dorsiflexion or plantarflexion at 0. /s to avoid stretch on peri-articular structures and reduce cues from the footplate following acceleration. They indicated when they detected movement at the ankle using a hand-held trigger that recorded the angle and verbally indicated the direction of movement. Strength: Maximum isometric plantarflexor and dorsiflexor strength was assessed using standard operating procedures for the dynamometer with the ankle in a neutral position (0 degrees ). For plantar flexion, participants pressed their foot downward as hard as possible against the footplate and then pulled it upward as strongly as possible (dorsiflexion). Falls Risk and Balance: The Standing Forward Reach Test is a well-established measure of balance and falls risk. The distance the participant can reach forward beyond arm s length while standing with an outstretched arm at shoulder height was measured Mobility: The 0-Metre Walk Test evaluated mobility ; participants walked this distance at their self-selected pace which was recorded with a stopwatch and velocity (m/s) calculated. Analysis and data processing: Paired t-tests compared the outcome measures with and without TENS. To obtain an insight into the clinical significance of any changes, the mean difference between the control and intervention and the percentage change (of the control value) for each parameter were calculated. RESULTS Twenty-nine stroke survivors were recruited, ( women), mean age of. (sd., range= -) years. Sixteen had a right sided hemiplegia, were left sided and two had a bilateral weakness (for whom stimulation was given to the weaker foot). Mean walking speed was

8 Page of Clinical Rehabilitation (sd 0.) m/s; eight (%) were physiological walkers, five (%) were household walkers, seven (%) were limited outdoor walkers and nine (%) were unlimited outdoor walkers according to the Walking Handicap Scale. All participants tolerated the stimulation and found it acceptable. One could not feel any stimulation even at maximum intensity and with the TENS sock dampened, however she continued with the testing and reported a positive effect with stimulation (which was borne out by the objective measurements). One participant reported that his leg was painful after the treatment but had resolved the next day; no other adverse events were reported. All parameters showed a significant improvement with TENS (p= ) except dorsiflexion strength (p=0.) and joint position sense (p=0.0) (Table ). DISCUSSION Our results show that it is feasible and acceptable to provide supplementary sensory stimulation using a TENS sock to stroke survivors while active, which warrants further investigation. One of our concerns in undertaking this trial was the possibility that supplementary stimulation while active could be detrimental and increase falls risk as it could increase the cognitive demands of perceiving and processing the additional afferent information which could detract from the attention available for balance and mobility tasks thereby increasing the potential for falls or could have interfered with the afferent signals from the joints so that movement was not perceptible. This was not the case; balance improved indicating a reduction in falls risk, an improvement in plantarflexion was seen nad

9 Page of no effect on dorsiflexion. Only one (minor) adverse event was reported. Thus we plan to develop active TENS during every-day activities with further trials. Limitations: This was an exploratory trial of the immediate effects of active TENS. It fulfilled its aims and showed that active TENS could affect strength, proprioception, balance and mobility which support further trials to develop the intervention, particularly to investigate the effects of longer-term use before progressing to a definitive trial. However, inference cannot be drawn about the effects (or effectiveness) of its use during rehabilitation, the acute stages of recovery, or of prolonged use. The data indicate a variable response to the intervention so, although we would recruit a pragmatic sample in the first instance, further work is needed to identify characteristics of stroke survivors who are likely to benefit from activetens and to identify the most effective dose of stimulation in terms of the intensity, frequency and burst pattern of the electrical stimulation. Previous studies have shown that a single 0 minute session of TENS can improve function immediately afterwards,0 but the current results are the first to assess the effects of TENS during stimulation and while mobile. They suggest that the effects of TENS are almost immediate. However the fact that we found a difference between stimulation and control conditions indicates that there is negligible carry-over effect once stimulation stopped and our evidence of effect is limited to the period of stimulation. The few previous trials of TENS to the lower limb which have included a follow-up period provide conflicting results,,. Sonde et al and Yan & Hui-Chan found that the effect of TENS was lost at follow up but Shamay et al reported sustained changes. These were stronger in the group who received task-related training plus TENS rather than TENS alone, suggesting that TENS needs to be combined with activity to optimally sustain changes in performance. This supports the notion of using TENS during every-day activity. Dose-response studies are needed to establish the amount and duration of stimulation needed to produce sustained change. It is possible that

10 Page of Clinical Rehabilitation TENS does not facilitate sustained changes in motor function, but could still be used in the long-term to provide an orthotic, rather than curative effect. CLINICAL MESSAGE ATIVETENS ActiveTENS using a sock electrode is a feasible and acceptable way to provide supplementary sensory stimulation to chronic stroke survivors and shows promise as potential intervention to improve strength and joint position sense, balance and mobility. Further trials to develop the intervention are warranted. Initial concerns that ActiveTENS could have a detrimental effect and increase the risk of falls was not supported.

11 Page 0 of Competing interests: none Source of funding: Dr Sadeghi was supported by a University of Salford Overseas Contributors. SFT initiated the study, designed it, monitored progress, oversaw the data analysis and lead the preparation of the manuscript and is the guarantor, EDS designed the study, undertook the data collection and analysis and contributed to the preparation of the paper CJN contributed to the initiation, design, data collection processes, analysis and preparation of the manuscript

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16 Page of Clinical Rehabilitation Table. The effects of TENS on mobility, balance, strength and proprioception in people with stroke Mean (sd) Forward Reach (cm) Control =. (.) TENS =. (.) Velocity (m/s) Control = 0. (0.) TENS = 0. (0.) Plantarflexor strength (Newton/m) Dorsiflexor strength (Newton/m) JPS plantar flexion (degrees) JPS dorsiflexion (degrees) Control =. (.) TENS =0. (.) Control =. (.) TENS = 0. (.) Control =. (.) TENS =. (.) Control =. (.) TENS =. (.) Mean difference (% difference). (.) 0.% (.) 0.0 (0.0).% (.). (.).% (.0). (.).% (.) -.0 (.) -.% (.). (.).% (.) P values (% CI) 0.00 (-., -0.) 0.00 (-0.0, -0.0) 0.00 (-., -.) 0. (-., 0.) 0.0 (0.,.) 0.0 (-0.,.) N.B a negative value for joint position sense indicates an improvement (in that the movement was detected after less joint movement)

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